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Tests in pregnancy
Published by Bupa's Health Information Team
The aim of tests during pregnancy (antenatal tests) is to monitor the health and wellbeing of the mother and developing baby (fetus). Some antenatal tests are routinely offered to all women and others are offered only to certain women because of their age and medical or family history.
The first test of any pregnancy is one that confirms the woman is pregnant. Conception typically takes place midway through a woman's menstrual cycle. Pregnancy tests are very accurate and can usually detect pregnancy from the time a woman misses her first period - approximately two weeks after conception. Women can buy home-testing kits from a pharmacy, or take a urine sample to their GP surgery.
Check-ups during pregnancy
Once a woman knows or suspects she is pregnant, she can make an appointment with her GP to discuss antenatal care and tests. The GP will ask about any previous pregnancies, general health and whether any close members of the family have a health problem that can be inherited, such as cystic fibrosis.
The GP checks that the woman is taking the right dose of folic acid supplement (400 micrograms a day) and gives general advice about pregnancy. A referral is made for antenatal care throughout the pregnancy. This could be at a hospital, at the GP surgery, in a clinic or at home (although any scans will need to be in a hospital).
Booking visit (first appointment)
The first appointment usually takes place at around 10-13 weeks. This is a detailed antenatal visit and may take some time. Some women need two appointments to cover everything. Women may see a midwife, a doctor or both. The woman's health, previous pregnancies, any medical problems and social circumstances are discussed.
An estimated date is given for when the baby is due. A brief ultrasound scan is performed to confirm that the size of the baby fits with the estimated dates and to check if the woman is expecting more than one baby.
The midwife or doctor takes a blood sample. Although there may be some variation between different healthcare providers, the following are the typical blood tests done at the booking visit:
- blood group and rhesus (Rh) type. Women are either Rh positive or negative. Rh negative women are usually offered an injection after delivery to protect their next baby from the risk of anaemia
- haemoglobin to check for anaemia
- screening for infections that can affect the mother and baby, such as hepatitis B or syphilis and HIV
- immunity to rubella (german measles). Women who are found not to be immune are given advice on how to reduce the risk of catching it and what to do if they catch it
Other blood tests may be offered depending upon a woman's medical history and ethnic background.
The woman's height and weight are recorded. Women who are underweight or overweight may need extra care.
A pelvic examination (internal) is not usually needed although women may be offered a smear if this is not up-to-date, or swabs if there have been symptoms of vaginal infection. The midwife usually feels the abdomen.
Arrangements for antenatal care can vary but the National Institute of Clinical Excellence (see Further information) advises that healthy women have up to 10 check-ups for a
first pregnancy, including the booking visit. Women who have had previous healthy pregnancies need only seven. At each appointment blood pressure and urine are tested and the baby's development is checked.
Checking the mother's health
Blood pressure is monitored as this can rise during pregnancy. Urine is tested for infection and for the presence of protein. Protein in the urine and raised blood pressure are two signs of pre-eclampsia - a symptomless condition that can be harmful to both mother and baby and may mean that the baby needs to be delivered early. Blood is tested again at 28 weeks for anaemia.
Checking the baby's development
As the baby grows, the uterus rises out of the woman's pelvis and becomes the "bump". The top of this is called the fundus. The height of the fundus is measured to ensure that the baby is growing.
The baby's heartbeat is not routinely checked, but some mothers may ask to listen to it for reassurance. The midwife or doctor may use a device placed on the abdomen to amplify the heartbeat.
At around 19-20 weeks, women start to feel the baby moving. Babies have active and restful times. In the early months, they have plenty of room and may move around a lot. As the pregnancy progresses, the midwife or doctor will ask about the baby's movements and try to determine the position of the baby by feeling the mother's abdomen. Towards the end of pregnancy, the head usually drops down into the pelvis into a position ready for delivery (when the head is said to be engaged).
Checking for abnormalities
Over 95% of pregnancies in the UK result in the birth of a healthy baby. However, if there are any problems, knowing about them in advance can help parents and doctors plan for the baby's future and assess any special requirements for the birth and aftercare. For some conditions that cause physical and mental problems there is no cure, and if the baby is affected some women may wish to have a termination of their pregnancy. Women will be supported by their health carers, whatever they decide.
Various tests may be offered to check the health of the baby. Screening tests assess the risk of the baby being born with certain conditions, such as spina bifida or Down's syndrome, but cannot give a definite "yes" or "no" diagnosis. The overall calculation of risk may include more than one type of screening test plus the woman's age.
Other tests can confirm whether the baby has a certain condition.
For many women, the decision to have these tests is a difficult one: it's important to consider what it would mean if the results were abnormal.
Blood tests are offered from 11-20 weeks. The levels of a number of chemicals can be measured in the mother's blood to help estimate the risk of the baby suffering from certain conditions, such as spina bifida or Down's syndrome.
Different tests measure different hormones or proteins, or combinations of these, including alpha-fetoprotein (AFP), human chorionic gonadotrophin (hCG), oestriol and inhibin A. If hCG and AFP are used as a screening test, this is often called the "double test". If oestriol is added to the double test, this is known as the "triple test". If inhibin A is added to the triple test, it becomes the "quadruple test".
In early pregnancy, as well as checking the size of the fetus and looking for more than one baby, ultrasound is used to diagnose early complications such as miscarriage.
At 18-20 weeks of pregnancy, most women have a more detailed ultrasound scan. The ultrasonographer makes sure the right amount of fluid surrounds the baby, examines the baby's head, heart, spine, limbs and internal organs in detail and checks the position of the placenta (which joins the mother and fetus and allows exchange of nutrients and waste products between them). This scan can identify some physical abnormalities, such as cleft lip or skeletal abnormalities, and can confirm spina bifida if blood tests have shown the baby is at high risk. It cannot diagnose Down's syndrome.
Nuchal translucency scan
This is a screening test for Down's syndrome that's usually offered at 11-14 weeks. It involves an ultrasound scan to measure the thickness of the layer of fluid at the back of the baby's neck. Babies with Down's syndrome have a thicker layer. If it is thicker than average, women are usually offered an amniocentesis for diagnosis.
Amniocentesis is a diagnostic test that some women choose to have, usually between 15 and 19 weeks of pregnancy. A fine needle is inserted into the amniotic fluid surrounding the baby. Ultrasound is used to guide the positioning of the needle. The amniotic fluid contains some cells from the baby that are cultured in the laboratory and then analysed in detail. Full results can take up to four weeks.
This is an accurate way of finding out whether the baby has a number of genetic or inherited disorders, such as Down's syndrome or cystic fibrosis. Amniocentesis carries a 0.5 -1% risk of harming the baby or causing a miscarriage. It is usually only offered to women when screening tests show they may be at a higher risk of having a baby with a genetic disorder, or to women over 35 years old. For more information, please see the separate Bupa factsheet on Down's syndrome.
Chorionic villus sampling (CVS)
For CVS, a fine instrument is inserted through the woman's cervix into the uterus and a sample of the chorionic villi (tiny fingerlike projections found in the placenta) is removed. These have the same genetic material as the baby.
This test looks for similar problems as amniocentesis, although it does not test for neural tube defects. CVS is performed earlier - usually between 10 and 12 weeks of pregnancy, and the results are usually available within a few days. The results are not quite as accurate as amniocentesis, the procedure is technically quite difficult and it is not always successful. There is a slightly higher risk of miscarriage with CVS - approximately 1-2%.
National Institute for Clinical Excellence (NICE)
Routine antenatal care for healthy pregnant women.
Informed Choice - MIDIRS